Diamond

How Products Are Made
COPYRIGHT 1996 Gale Research Inc.

Diamond

Background

The diamond is the hardest natural substance known. It is found in a type of igneous rock known as kimberlite. The diamond itself is essentially a chain of carbon atoms that have crystallized. The stone's unique hardness is a result of the densely concentrated nature of the carbon chains. Like other igneous rocks, kimberlite was formed over the course of thousands of years by volcanic action that occurred during the formation of the earth's crust. Kimberlite is located inside these former spheres of volcanic activity—often near mountain ranges—in vertical shafts that extend deep inside the earth. Inside the kimberlite are intermittent deposits of diamonds, one of several minerals present. However, not all kimberlite contains diamond. Other stones often found with diamonds are mica, garnet, and zircon. Kimberlite may be blue-grey in hue—thus termed blue ground—or if exposed to air it may have a yellowish cast and is called yellow ground.

History

It is thought that diamonds were first discovered in Indiaabout 6,000 years ago in the riverbeds of the region. Traders were responsible for bringing the gems as far east as China and as far west as Rome during the classical and early medieval eras. The Chinese were the first to hamess the unusually tough nature of the gem and used it as a tool to cut other stones. Pliny the Elder, a Roman scholar, wrote about the diamond in the first century. The word itself stems from the Greek term adamas which means "invincible" or "unconquerable."

From the earliest days, the diamond has been imbued with mystery and superstition. Because they were so rare—at first found only in India—it became a commonly held superstition that the diamond lent its wearer special powers. They were worn in battle to insure victory and sometimes invoked as an antidote to poison. Other superstitions associated with the stone included the caveat that placing it in the mouth would bring on a loss of teeth. In other cases, finely ground diamond, made into a powder, was thought to be an effective poison. Indeed, experts agree that even in a pulverized form, the unique sharpness of the mineral would tear minuscule holes in the digestive tract. Because it is both the hardest and one of the rarest natural substances, diamonds have always fetched exceedingly high prices. The extreme value of the stone also made it a portable form of wealth in times of warfare and upheaval.

The actual mining of diamonds as an industry can be traced back to India to around 800 to 600 b.c. India was the only known source of the rocks for over a thousand years, until they were unearthed in Borneo around a.d. 600. During the Middle Ages, the diamond was overshadowed by some of the more colorful gems like the ruby and emerald. These other stones found their way into the jewelry of the rich and powerful of Europe more easily than the diamond. Additionally, gem-cutting techniques had not yet been developed to unleash the brilliance of the stone. Diamonds were usually left in their natural state or shaped by a rudimentary cut. In the 17th century, how-ever, a Venetian lapidary named Vincenzo Peruzzi developed the so-called brilliant cut. This cut revealed the intricacies and the natural perfection of the stone.

In the 18th century, diamond deposits were discovered in Brazil in small quantities, and later in Australia, Russia, and the United States. Brazilian gems were first taken to India and shipped to Europe as Indian diamonds, since people considered non-Indian gems less valuable. In the 20th century, an American mine near Murfreesboro, Arkansas, was open for novelty public mining for a small fee. High-quality diamonds have been found in Siberia, but the extremely cold temperature has made large-scale mining unfeasible.

In 1866 the world's largest cache of diamonds was discovered in South Africa. Some children had found a rock and brought it home, and a curious neighbor passed it on to a trader, who gave it to a geologist. It was discovered to be a diamond of enormous size and worth a small fortune. South Africa soon experienced a diamond rush, and shanty towns sprang up with the influx of prospectors. Eventually, the various mines and mine companies of the region were consolidated under the control of the DeBeers organization. With the DeBeers Consolidated Mines, Ltd., a Central Selling Organization, and a Diamond Trading Company, this conglomerate controls about 80% of the world's diamond output. Contemporary diamond mining is centered at Kimberley, South Africa, and carried out by DeBeers. Every six weeks or so, representatives of the DeBeers Diamond Trading Company invite a special list of diamond wholesalers—less than a hundred world-wide—to London to view preselected lots of the gem. This is the only method by which South African DeBeers diamonds come onto the market.

Industrical Applications

In modern times diamonds have become indispensable to industry. Automobile magnate Henry Ford was the first to uncover the contemporary industrial uses of the stone. He sponsored research into its applications for the manufacturing sector, especially as a low-cost abrasive, and the Detroit area became a hub for dealers of diamond tools. The aircraft industry followed the lead of the automotive sector, becoming an avid user of diamond-based products. Diamonds used for industrial applications are usually of a lower grade than those found in the gemstone market, but they retain the same properties of hardness and durability. Diamond
tools last much longer than those made from other sources and offer a nearly unmatched precision in cutting other substances. Additionally, such tools work faster and much more quietly than other alternatives.

Tools made from industrial diamonds are used in the mirror and optical manufacturing fields as well as in gas and oil drilling endeavors. In the textile industry, devices made from diamonds are used to cut patterns. In medicine, cutting instruments made from diamonds are used to cleanly slice bone and tissue. The construction industry uses diamond tools in the grinding and cutting of concrete and pavement. Diamonds are also used to make needles for stereo record players.

Physical Characteristics

Diamonds are chains of carbon. Carbon is one of the most common substances on the planet. In one form it is simple graphite, used in pencils, but in its crystallized form, it takes an altogether different appearance as diamond. On the scale used by mineralogists to measure the hardness of minerals, diamonds rate ten on a scale of one to ten. Diamonds are measured in carats, the standard unit of measurement for gemstones. One carat is roughly equal to one-fifth of a gram. The carat can be further divided into points based on a scale of 100. One of the reasons diamonds are so prized is because the light they absorb is reflected directly back outward, if the stone has been properly cut. The unusual crystal structure of the gem allows this high degree of refractability. Because of their structure, diamonds are also excellent conductors of electrical current.

Structurally, the diamond can be described as an octahedron. This means that there are double four-sided pyramids of carbon chains inside that meet one another at the bases. Cubes or dodacahedrons—a twelvesided
shape—are also found within the stone. Sometimes small triangular pockets called trigons can be observed.

Diamonds are found in nature in a variety of hues. Colorless or white diamonds are the most common, while some tinted stones are rare and valuable. The shades may be yellow, blue, pink, green, or amber. In South Africa it is common to see orange diamonds as jewelry, but this is a custom that has not made its way into the rest of the world. Some of the world's most famous diamonds are the colored ones—the heavy Dresden Green, for instance, and the infamous Hope Diamond. The latter, blue in color, is thought to hold certain negative energy, and many unexplained deaths have been associated with its owners. It is now in the collection of the Smithsonian Institution in Washington, DC.

Extraction and Refining

Diamonds are mined either from the kimberlite pipes below the earth's surface, or from alluvial deposits. Alluvial (riverbed) deposits occurred when volcanic action carried kimberlite and other minerals from the center of activity to naturally forming irrigation systems. Such diamonds are found quite near the earth's surface. In alluvial mining, considerable amounts of sand must first be removed from the area. The sand and other such components are called over-burden, and large mechanical scrapers are used to move it out of the way. Underneath the overburden lies a gravel bed, and bulldozers scoop the gravel up and set it aside in piles.

The piles are then taken to a screening plant, where the diamonds are extracted. In alluvial mining, it is sometimes necessary to reach the bedrock underneath the gravel bed—or sometimes even below the bedrock itself—in order to unearth the diamond deposits. The bedrock must be thoroughly searched. Sometimes an enormous vacuum device called a Vacuveyer is used for this purpose. As the mining process moves along in a horizontal fashion, the removed overburden is again deposited to fill over the excavated sites.

Below-ground mining of kimberlite for diamond also requires moving enormous quantities of rock and other material in order to unearth gems, but on a much larger scale than alluvial mining. For one part diamond uncovered, it is estimated that 15 to 30 million parts waste must be moved out of the way. Unlike mining endeavors for gold or other substances, engineers cannot determine beforehand whether an area has a large abundance of diamond.

Mining

1 Block caving is the most commonly used method in excavating diamonds from kimberlite deposits. This method offers the highest yield and thus is the most cost effective. First, a large vertical hole is excavated, typically 1,750 feet (533 m) in diameter. Levels are placed approximately every 40 feet (12 m). Along these levels are horizontal tunnels known as scraper drifts. In the drifts, there are small inclined coneshaped openings at intervals of every 11 feet (3 m) or so. These openings are roughly four feet by four feet. When a horizontal slice is cut above the cones—usually about six feet (1.8 m) in height—the kimberlite begins to break off and fall into the cone and into the scraper drift. The material is then pushed onto trucks. The trucks travel underground through the mining area and take the collected kimberlite to a crushing device.

Crushing

2 In the crushing operation, which occurs in the below-ground mining facilities, large chunks of kimberlite are broken up into more easily transportable segments. After an initial crushing, the kimberlite passes through a grizzly, or a set of iron bars. If the crushed chunks do not pass through the grizzly, they are still too large, and they are sent back for further crushing. The crushed kimberlite is then taken above the surface for further processing. When no more kimberlite is found entering the cones, the area is depleted and work moves on to a lower level.

Separating

3 The actual diamonds must be separated from the rock that surrounds them.
Crushing or milling the excavated material is the first step, but this is done in a rudimentary form so as not to damage the potential gems inside. Next, a gravity-based device is used to sort the diamond-containing portions—called the concentrate—from the tailings, or the filler rock. One of the most commonly used methods to separate the two is a type of washing pan developed in South Africa in the 1870s. Decomposed kimberlite and water—in a mixture known as a puddle—is put into the pan. The mixture's viscosity is a crucial element, because the lighter particles will rise to the top, but the diamonds and other heavy minerals will descend to the bottom of the pan.

Another method of uncovering diamonds uses media separators. A stew called a slurry is made up—typically consisting of water added to the crushed concentrate and tailings. Ferro-silicon powder, which has a heavy density, is also added.

The slurry may be put into one of three types of media separators. The first is a cone-shaped tank, with a cone-shaped agitating element inside. The agitator moves around the sides of the tank, but leaves enough room so that the lighter tailings can rise to the top and the heavier elements sink to the bottom. In a lifting-wheel type of media separator, a wheel is filled halfway with slurry. Paddles inside it agitate the mixture, and lift the heavy particles from the bottom and separate them from the rest of the mixture. The third type of media separator is known as a hydrocyclone. It is a large vat that spins around, and through centrifugal force, the heavier, diamond-rich particles are separated.

Greasing

4 After this rudimentary separation, the concentrate moves to a greasing area, another innovation in diamond manufacturing developed in South Africa in the late 19th century. Mixed with water, the kimberlite-and-diamond mixture is placed on a greased belt or table. This device is usually slanted and vibrated. The method operates on the premise that diamonds newly excavated will not become wet when brought into contact with water. Instead they will stick to the grease. Petroleum jelly is usually the preferred substance on the grease belt or table. The water then carries away the remaining non-diamond particles. The diamond-laden concentrate is then swept off the table and boiled to remove the traces of grease. In a newer method, X-ray technology is used to determine which of the concentrate is diamond and which is effluvial material.

Cutting

5 Chunks of diamond eventually become small, perfectly shaped gemstones commonly used in engagement rings and other jewelry. Since diamond is the hardest known substance, diamond dust must be used to cut the stone. In cutting, a minuscule groove is incised into the surface of the diamond, and a cleaving iron is inserted into the groove. With a quick, forceful blow, the diamond should split perfectly along its naturally occurring planes. The lapidary determines further cuts by marking them off on the surface with ink. Next, a diamond saw, oiled with the unusual combination of diamond dust and olive oil, is rotated vertically on the surface of the raw gem. This device divides the diamond into new segments. These parts are then fed into a lathe-like device for grinding.

The Future

Diamonds are a finite resource. The fate of Indian diamonds is a good example of what the future might hold for the South African diamond-mining industry. From the first discovery of the gems in India until relatively recently, it is thought that over 12 million carats originated from India. By the mid-20th century, the resources were nearly depleted, and India was producing only about 100 carats annually. Diamonds will continue to be used in industry and high-technology enterprises, but synthetically produced facsimiles—first manufactured in 1953—may accomplish some of the tasks originally the exclusive province of the real stone. These "manufactured" gems have the same properties of hardness and durability, and while they will never be as popular as the real diamond for adomment purposes, they are well suited for industrial applications.

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Diamond, David

Contemporary Musicians
COPYRIGHT 2004 Gale, a part of Cengage Learning

David Diamond

Composer, educator

The American composer and teacher David Diamond wrote in a wide variety of styles and in virtually every medium. The strength of his music lay in its imposing formal design and its serious expression, although it also embodied lyrical warmth and romanticism. Diamond was one of a group of composers who forged a distinctly American idiom of classical music in the middle of the twentieth century. He lived long enough to see his music fall out of favor due to the influence of the European-devised 12-tone system, and then to witness its revival during the more eclectic scene at the end of the twentieth century.

David Diamond was born on July 9, 1915, in Rochester, New York. He was the son of Austrian-Polish Jewish immigrants who could not afford to cultivate the musical aptitude that their son showed from about the age of six. Fortunately, the young boy's abilities also impressed others who were in a better position to help him. At a public school in Rochester, he received a violin and free lessons, and in 1927, when the family moved to Cleveland, André de Ribaupierre taught him violin and theory without remuneration at the Cleveland Institute of Music.

Upon returning to Rochester in 1929, Diamond entered the preparatory department of the Eastman School of Music on a scholarship, studying violin with Effie Knauss and composition with Bernard Rogers. He continued at Eastman as an undergraduate after finishing high school in 1933, but left after one year to move to New York. Again on a scholarship, he studied the Dalcroze method of Eurhythmics with Paul Boepple and composition with Roger Sessions at the New School from 1934 to 1936, and continued privately with Sessions until 1937.

Diamond made three trips to Paris in the mid-to-late 1930s (the last through funds from the first of three Guggenheim Fellowships), where he studied with the famous French teacher Nadia Boulanger and met many of the great artists then living in Paris, such as Albert Roussel, Igor Stravinsky, Maurice Ravel, André Gide, and Charles Munch. Important compositions from these Paris years include the first of his three violin concertos (1936, 1947, and 1967); Psalm for orchestra (1936), his first work to receive wide attention and also the Juilliard Publication Award in 1938; a cello concerto (1938); and Heroic Piece (1938) for small orchestra. He applied for a job teaching at Columbia University in 1938 but was turned down, and he recalled to Chris Pasles of the Los Angeles Times that he was told he should "stop wearing turtleneck sweaters," which he believed was an indication that he should keep his homosexuality in the closet.

Germany's declaration of war on France in 1939 brought Diamond back to the United States for most of the next 12 years. At first he had to scramble financially, working the night shift at a soda counter and then landing a spot as violinist in the orchestra of the weekly Hit Parade radio show. During this time he composed both chamber and orchestral works, and their performance attracted financial support from foundations and other funders. Among his chamber works of the period are the first three of his eleven string quartets; a piano quartet for which he won the Paderewsky Prize (1938); a concerto for two solo pianos (1942); a sonata for piano (1947); and a Chaconne for violin and piano (1948). Orchestral works of the period include the first four of his eight symphonies; The Dream of Audubon, a ballet (1941); music for Shakespeare's The Tempest for orchestra (1944); Rounds for string orchestra (1944); music for Shakespeare's Romeo and Juliet for orchestra (1947); and a piano concerto (1950).

Diamond lectured on American music in Salzburg during the summer of 1949, and two years later went to Italy on a Fulbright Fellowship. His motivations for leaving were complex. Diamond's brand of accessible orchestral music was being temporarily eclipsed by the difficult, rigorously intellectual 12-tone method. He also pointed to anti-Semitism and resistance to his open homosexuality as reasons for a decline in the performance of his works in the United States, and he was dismayed by a subpoena to appear before the U.S. House of Un-American Activities Committee. He stayed in Italy, first in Rome and then in Florence, for 14 years, returning to the United States on two occasions (1961 and 1963) to teach at the State University of New York at Buffalo as Slee Professor of Music. The years in Italy proved musically productive for Diamond, who composed works including The Midnight Meditation, a cycle for voice and piano (1951); a piano trio (1951); string quartets 4-8; symphonies 5-8; sonatas for solo violin (1954) and for cello (1956); Sinfonia Concertante (1954–1956); The World of Paul Klee for orchestra (1957); a woodwind quintet (1958); The Sacred Ground for baritone, chorus, children's chorus, and orchestra (1962); and Elegies for flute, English horn, and strings (1963).

Returning to the United States in 1965, Diamond became chair of the composition department at the Manhattan School of Music; he resigned in 1967. A position as composer-in-residence at the American Academy of Rome drew him back to Italy during 1971 and 1972. After 1973 he was professor of composition at the Juilliard School of Music in New York. Some of his better-known compositions from the years 1964 to 1984 were We Two (1964), Hebrew Melodies (1967), and The Fall (cycles for voice and piano, 1970); Music for Chamber Orchestra (1969); The Noblest Game, (an opera, 1971–1975); a piano quintet (1972); and Ode to the Morning of Christ's Nativity for a cappella chorus (1980).

Several writers have suggested that the early 1950s marked a rather abrupt change to a dissonant and nontonal style, some even stating that Diamond had taken up the 12-tone method. Diamond himself refuted this last statement in an article appearing in the New York Times, saying, "I am not now and never have been a 12-tone composer." He even commented to Matt Schudel of the Washington Post: "I hated all that avant-garde stuff. It was all wrong. They don't write out of love." While his music became gradually less tonal in later years, he always commanded a variety of styles, which he used according to the function of the music. The music for Broadway productions of Shakespeare plays, for instance, was quite lush and tonal, while the more absolute works, such as the fourth symphony, frequently involved a more complicated language (here polytonality). As the grip of the 12-tone system over American compositional life began to loosen, Diamond's works enjoyed a revival in popularity. He was championed by conductors such as Leonard Bernstein and by Seattle Symphony music director Gerard Schwarz.

The 1980s and 1990s saw works such as the ninth symphony in a series that Diamond had begun nearly 45 years earlier. The symphonies were introduced steadily from 1940 until 1965, but it was not until 1985 that Diamond finally unveiled the ninth. In 1996, the Juilliard Orchestra performed the world premiere of Diamond's Concerto For String Quartet and Orchestra, which the Juilliard School commissioned from Diamond in honor of the 50th anniversary of the Juilliard Quartet. The performance met high praise, notably from the Village Voice's Leighton Kerner, who wrote, "American music boasts no composer more brilliant or more melodically imaginative, and this new concerto bears out the fact." Even at 81 years of age, Diamond seemed to have boundless reservoirs of creativity and energy.

Modern rhythmic complexities energized his later compositions such as Warning for chorus and tubular bells (1973). While thus embracing some of the innovations of the twentieth century, Diamond rejected others, most emphatically the aleatoric or chance music of John Cage and his followers. Reflecting on his career, Diamond commented, "One hopes the future will bring my music to a larger audience, one not interested in Trends and The Now, but music for All Time, for all humanity." He remained active into old age, completing his Symphony No. 11 in 1991 in response to a commission from the New York Philharmonic Orchestra on the occasion of its 150th anniversary. Diamond died in Rochester on June 13, 2005.

For the Record …

Born on July 9, 1915, in Rochester, NY; died on June 13, 2005, in Rochester, NY. Education: Attended Cleveland Institute of Music; Eastman School of Music; New School, New York City; studied composition privately with Roger Sessions and with Nadia Boulanger.

Worked night shift at soda counter, New York, 1939; played violin in Hit Parade radio orchestra, early 1940s; works widely performed by American symphony orchestras, 1940s; moved to Rome, 1951; taught at Rome University, early 1950s; lived in Florence, Italy, early 1950s–1965; taught at University of Buffalo, 1961, 1963; returned to U.S., taught at Manhattan School of Music, 1965–67; professor of composition, Julliard School, New York City, 1973–86.

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diamond

diamond a precious stone consisting of a clear and colourless crystalline form of pure carbon, the hardest naturally occurring substance, taken as a type of brilliance or excellence. The word is recorded from Middle English, and comes via Old French from medieval Latin diamas, diamant-, variant of Latin adamans, from the base of the English word ‘adamant’.

Diamond is also used for a figure with four straight sides of equal length forming two opposite acute angles and two opposite obtuse angles, a rhombus, and diamonds are thus one of the four suits in a conventional pack of playing cards, denoted by a red figure of such a shape.

Diamond was the name of Isaac Newton's dog, which according to a (probably apocryphal) story knocked over a candle which set fire to some papers and thereby destroyed the finished work of some years.Affair of the Diamond Necklace a political scandal in 18th century France. Queen Marie Antoinette was said to have purchased a valuable necklace and subsequently denied any knowledge of the matter. Although the affair was an attempt by a French adventuress to acquire the necklace by a pretence of acting on behalf of the Queen, and Marie Antoinette was not involved, the Queen's innocence was not believed, and the scandal contributed materially to her unpopularity.diamond cuts diamond only a diamond is hard enough to cut another diamond, used of persons who are evenly matched in wit or cunning. The saying is recorded from the early 17th century, but an earlier related usage is found in Nashe's Christ's Tears (1593), ‘An easie matter is it for any man to cut me (like a diamond) with my own dust.’diamond jubilee the 60th anniversary of a notable event, especially a sovereign's accession or the foundation of an organization.Diamond Sculls an annual single-scull race at Henley Royal Regatta, instituted in 1844, for which the prize was a gold pin ornamented with gold sculls and a drop diamond.Diamond State an informal name for the state of Delaware, said to be so named because it was seen as small in size but of great importance.diamond wedding the sixtieth anniversary of a wedding.

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diamond

dia·mond
/ ˈdī(ə)mənd/
•
n.
1.
a precious stone consisting of a clear and typically colorless crystalline form of pure carbon, the hardest naturally occurring substance. ∎
a tool with a small stone of such a kind for cutting glass.
∎
in extended and metaphorical use with reference to the brilliance, form, or hardness of diamonds:
the air glitters like diamonds.2.
[often as adj.]
a figure with four straight sides of equal length forming two opposite acute angles and two opposite obtuse angles; a rhombus:
decorative diamond shapes. ∎
(diamonds)
one of the four suits in a conventional pack of playing cards, denoted by a red figure of such a shape.
∎
a card of this suit:
she led a losing diamond. ∎
the area delimited by the four bases of a baseball field, forming a square shape.
∎
a baseball field.
PHRASES:diamond in the rough
a person who is generally of good character but lacks manners, education, or style.DERIVATIVES:dia·mond·if·er·ous
/ ˌdī(ə)mənˈdifərəs/ adj.

Cite this article Pick a style below, and copy the text for your bibliography.

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Diamond

Encyclopedia of Occultism and Parapsychology
COPYRIGHT 2001 The Gale Group Inc.

Diamond

This gem was believed to possess the most marvelous virtues. It gave victory to whomever carried it on his left arm, whatever the number of his enemies. Panics, pestilences, enchantments were all said to fly before it; hence, it was good for sleepwalkers and for the insane. It deprived the lodestone of its virtue, and one variety, the Arabian diamond, was said to attract iron more powerfully than a magnet.

The diamond is the hardest substance known, a property referring to its resistance to being scratched, rather than its resistance to other forces, such as the strike of a hammer. Ancient peoples believed that neither fire nor blows would overcome its hardness, unless the diamond was macerated with fresh goat's blood. Cyprian, Austin, Isidore, and other church fathers, adopting this notion, used it to illustrate the method by which the blood of the Cross softens the heart of man.

If bound to a magnet, the diamond, according to the belief of the ancients, would deprive it of its magnetic property.

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diamond

diamond Crystalline form of carbon (C). The hardest natural substance known, it is found in kimberlite pipes and alluvial deposits. Appearance varies according to its impurities. Bort, inferior in crystal and colour, carborondo, an opaque grey to black variety, and other non-gem varieties are used in industry. Industrial diamonds are used as abrasives, bearings in precision instruments such as watches, and in the cutting heads of drills for mining. Synthetic diamonds, made by subjecting graphite, with a catalyst, to high pressure and temperatures of c.3000°C (5400°F) are fit only for industry. Diamonds are weighed in carats (0.2gm) and points (1/100 carat). The largest producer is Australia. Hardness 10; r.d. 3.5.

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diamond

diamond, mineral, one of two crystalline forms of the element carbon (see allotropy), the hardest natural substance known, used as a gem and in industry.

Properties

Diamonds crystallize in the isometric system (see crystal) commonly as transparent to translucent white, colorless, yellow, green, blue, pink, or brown octahedrons (the familiar diamond shape). The extraordinary brilliancy of diamonds after faceting is due to their very high refractive index, which is greater than that of any other naturally occurring gemstone. In addition to the gem varieties there are bort, which is poorly crystallized or of inferior color and in fragmentary condition, and carbonado (black diamond), which is gray to black and opaque, with poor cleavage. Bort and carbonado are used as abrasives, in the cutting of diamonds, and for the cutting heads of rock drills. Diamond abrasives may have been used as early as 2500 BC in China.

Natural Occurrence and Processing

Diamonds are found in alluvial (loose earthy material deposited by running water) formations and in volcanic pipes, filled for most of their length with blue ground or kimberlite, an igneous rock consisting largely of serpentine. At the surface the blue ground is weathered to a clay called yellow ground. Diamantiferous (or diamondiferous), or diamond-yielding, earth is mined both by the open-pit method and by underground mining. After being removed to the surface, it is crushed and then concentrated. Sorting is done by passing the concentrated material in a stream of water over greased tables. The diamond, being largely water repellent, sticks to the grease, but the other minerals retain a film of water, which prevents them from adhering to the grease. The diamonds are then removed from the grease, cleaned, and graded for sale.

Sources

The earliest sources of gem diamonds were India and Borneo, where they were found in river alluvium. All famous diamonds of antiquity were Indian diamonds, including the Great Mogul, the Orlov, the Koh-i-noor, and the Regent or Pitt. Other famous diamonds are the Hope (blue), Dresden (green), and Tiffany (yellow). In the early 18th cent., deposits similar to those in India were found in Brazil, mainly of carbonados, though they may have been known as early as 1670. In 1867, a stone found in South Africa was recognized as a diamond. Within a few years, this began a wild search for diamonds, both in river diggings and inland. In 1870–71, dry diggings, including most of the celebrated mines, were discovered. Well-known South African diamond mines are the Dutoitspan, Bultfontein, De Beers, Kimberley, Jagersfontein, and Premier. Russia, Botswana, Congo (Kinshasa), Australia, and South Africa are now the world's major diamond-producing nations; other important countries include Canada, Angola, Namibia, Ghana, and Brazil. The use of diamonds to finance African rebel groups and fuel civil strife led, in 2001 and 2002, to international agreements (the Kimberley Process) designed to certify legitimately mined diamonds, but in 2011 the permitted sale of diamonds from Zimbabwe, where the army has been accused of brutality and human rights violations in diamond mines and diamond revenues support an autocratic government, led to criticism of the certification process.

Synthetic diamonds were successfully produced in 1955; a number of small crystals were manufactured when pure graphite mixed with a catalyst was subjected to pressure of about 1 million lb per sq in. and temperature of the order of 5,000°F (3,000°C). Synthetic diamonds are now extensively used in industry.

The Diamond Cartel

The discoveries of 1870–71 in South Africa led to a great number of prospectors staking out claims and securing the diamonds by open-pit or quarry mining. The damage caused by floods and mudslides, unavoidable when there were so many different claims, was an important factor in the series of amalgamations carried on by Cecil Rhodes and Barnett Barnato. Rhodes brought about the merging of their interests in the De Beers Consolidated Mines, Ltd., which established (1889) an effective monopoly over the diamond industry. Loss of diamonds by theft was reduced through the passage of the so-called I.D.B. (Illicit Diamond Buying) Act, which limited the trade to licensed buyers and imposed penalties for the possession of uncut stones without a license. Thefts were further curtailed by the institution of compounds in which the workers live while employed by the company and which they leave only after being thoroughly searched.

Most of the major diamond producers belong to, or have cooperated with, the De Beers–led marketing cartel, formed to maintain the price of diamonds at a high level. De Beers, under Harry Oppenheimer's leadership (1957–84), maintained its dominant position in the industry by using its numerous worldwide companies to buy up new sources of diamonds and to control distribution of industrial diamonds and production of synthetic ones. In the last decades of the 20th cent., however, De Beers' hold over the unpolished diamond market decreased, and in 2000 the company announced it would end to its policy of controlling diamond prices through hoarding and shift its focus to increasing sales.

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Diamond, David

The Columbia Encyclopedia, 6th ed.

Copyright The Columbia University Press

David Diamond, 1915–2005, American composer, b. Rochester, N.Y. Diamond was trained at the Cleveland Institute of Music and the Eastman School; he also studied with Roger Sessions in New York and Nadia Boulanger in Paris. He composed in a variety of styles, beginning with neoclassical works in the 1930s and later developed an intensely lyrical neoromanticism. Diamond wrote much chamber music, including 10 string quartets; many preludes and fugues; songs and other vocal pieces; 11 symphonies; ballets and film scores; music for Shakespeare's Romeo and Juliet, The Tempest, and Timon of Athens; and Rounds (1944), for strings, his best-known work.

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